For electric motors with a collector such as direct current motors or universal motors, brushes, which are generally carbon-based, and are supported by the stator, come into electrical contact with the collector of the rotor, in order to ensure the electrical connection between the stator and the rotor. The brushes are fitted in a sliding manner in the brush-holders, and are thrust resiliently towards the collector by a spring which is provided between the base of the brush-holder and the brush. It is known to fit the brush-holders on a plate which is secured on the stator, with the plate having a central hole for the passage of the collector, and the brush-holders being arranged radially around the central hole, in order to position the brushes relative to the collector. Plates of this type are described for example in U.S. Pat. No. 7,256,527 B2, U.S. Pat. No. 8,395,297 B2 and JP 7-67296. In order to fit the brush-holders on the plate, the latter has notches or other guide elements with which the base of the brush-holders cooperates. The assembly is carried out by engaging the brush-holders on the plate from the central passage hole of the connector towards the periphery of the plate. The plate additionally has a stop for each brush-holder, in order to stop it radially in the direction of the periphery of the plate, which prevents the brush-holders from being able to collide against the housing of the motor.
However, these plates have the disadvantage of making the fitting of the brush-holders on the motor complex and problematic. In fact, in a first step, it is necessary to fit the brush-holders on the plate, and to insert the brushes in them, then, in a second step, to fit the plate which supports the brush-holders and the brushes on the stator of the motor, whilst making the collector pass through the central passage hole provided in the plate for this purpose. Thus, it is necessary to retain the brush-holders in position on the plate between the first step and the second step, which is generally obtained by fitting with clamped adjustment of the brush-holders on the plate, or by means of a retention unit which is provided on the plate, in order to retain the brush-holder in place on the plate. However, it is also necessary to retain the assembly of the brushes in the brush-holders between the first step and the second step, which is particularly problematic in practice, although once in place, it is no longer necessary to retain the brushes in the brush-holders, since it is the latter which will retain them in place.
The objective of the present invention is to provide a solution which makes it possible to simplify the fitting of the brush-holders and brushes on the stator of the motor.
For this purpose, the present invention proposes a starter for a thermal engine of a motor vehicle, comprising an electric motor, the electric motor comprising a brush-holder assembly for an electric motor, a collector, a head and a bearing, the brush-holder assembly comprising:
at least one brush-holder;
a support plate for this brush-holder for an electric motor, comprising:
a central passage hole for the collector of the electric motor;
guide elements which receive at least the brush-holder in sliding connection on the plate, according to a direction which is radial relative to the central passage hole, the plate being designed to permit fitting of the brush-holder in sliding connection on the plate, by engaging the brush-holder with the guide elements, in the direction going from the periphery of the plate towards the central passage hole;
the plate additionally comprising a non-return stop for each brush-holder after the latter has been fitted in sliding connection on the plate, in the direction going from the periphery of the plate towards the central passage hole, wherein:
the stop is resiliently retractable, in order to permit the fitting of the brush-holder in sliding connection on the plate, in the direction going from the periphery of the plate towards the central passage hole; and
after the brush-holder has been fitted in sliding connection on the plate, the stop opposes rigidly the displacement of the brush-holder, in the direction going from the central passage hole towards the periphery of the plate.
Thus, the brush-holder is fitted at the periphery towards the central passage hole, and is retained by the stop.
According to preferred embodiments, the brush-holder support plate according to the invention comprises one or a plurality of the following characteristics:
the brush-holder is spaced from the head. Just as the brush-holder which is fitted on the plate does not touch the head, the brush-holder does not transmit these vibrations directly to the head when the collector turns. In fact, the plate, which is preferably fitted between the bearing and the head of the electric motor of the starter, attenuates the vibrations in comparison with the case in which the brush holder is supported against the head of the motor of the brush-holder. This attenuation of the vibrations makes it possible to produce less noise. In fact, in the case in which at least one of the stops is the wall of the head, the head would give rise to greater noise;
wherein the plate is made of metal plate and the stop and the guide elements of the sliding connection are obtained from the plate, and are formed by cutting and by resilient deformation of the metal plate. Thus, the stop and the slide are less costly, and the weight is lighter;
the at least one stop is made of metal. Thus, because of the solidity of the stop, a single stop is necessary, and therefore the plate has smaller dimensions;
on a face perpendicular to the main face of the plate surrounding the passage, the brush-holder comprises an opening which allows a braid of the brush to slide throughout the service life of the brush, this being necessary when there is wear of the brush against the collector. Thus, the machine has an improved axial dimension;
the stop is designed to be retracted resiliently under the action of the brush-holder on the stop, during the fitting of the brush-holder in sliding connection on the plate, in the direction going from the periphery of the plate towards the central passage hole;
the stop is also designed such that, after the brush-holder has been fitted in sliding connection on the plate, the stop also opposes rigidly the displacement of the brush-holder in the direction going from the periphery of the plate towards the central passage hole;
the stop is produced in the form of a resilient blade which extends substantially radially relative to the central passage hole, the blade being arranged at one end on the plate on the side towards the periphery of the plate, the opposite end of the blade being free, and being arranged on the side towards the central passage hole, which opposite end is designed to come into contact with the brush-holder in order to oppose rigidly the displacement of the latter, in the direction going from the central passage hole towards the periphery of the plate, the stop being designed to be retracted resiliently by flexion of the resilient blade under the action of the brush-holder during the fitting of the brush-holder in sliding connection on the plate, in the direction going from the periphery of the plate towards the central passage hole;
the blade which forms the stop is designed to be retracted resiliently either in the direction of the face of the plate which is opposite the one which receives the brush-holder, or laterally relative to the direction of the sliding connection between the brush-holder and the plate;
the stop is integral with the plate;
the guide elements are integral with the plate;
the plate is obtained by cutting and resilient deformation of a metal plate.
According to another aspect, the invention also proposes a brush-holder for an electric motor which is designed to be fitted on a brush-holder support plate according to the invention, the brush-holder comprising:
a base which is formed such as to be able to engage the guide elements of the plate in sliding connection; and
a recess in the base which can be engaged by the non-return stop of the plate, in order to oppose the displacement of the brush-holder rigidly, at least in the direction going from the central passage hole towards the periphery of the plate.
According to a preferred embodiment, the brush-holder is designed to be fitted on a brush-holder support plate according to the aforementioned preferred embodiment, in which the stop is produced in the form of a resilient blade, the recess in the base of the brush-holder being provided in the lower face of the brush-holder, and the brush-holder comprising a chamfer which is provided in the lower part of the base, which chamfer is designed to engage the blade which forms the non-return stop of the plate, and to retract it resiliently during the fitting of the brush-holder in sliding connection on the plate, in the direction going from the periphery of the plate towards the central passage hole.
The invention also proposes a brush-holder assembly for an electric motor, comprising:
a brush-holder support plate according to the invention; and
at least one brush-holder which is received in the guide elements of the plate, wherein the non-return stop of the plate opposes the displacement of the brush-holder rigidly at least in the direction going from the central passage hole towards the periphery of the plate.
According to a preferred embodiment of the brush-holder according to the invention, the non-return stop of the plate is engaged in the recess in the base of the brush-holder in order to oppose the displacement of the brush-holder rigidly at least in the direction going from the central passage hole towards the periphery of the plate.